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Keys and Bearings.

'claw ' clutch, c is fixed by key to the right-hand shaft, and B
slides on a pair of feather keys D in the left-hand shaft, so that
the claws at A may be locked or unlocked. The clutch strap E
encircles the clutch B, and is further grasped by the fork lever:
this gives a sufficiency of wearing surface between the rotating
clutch and stationary lever. The difficulty of entering the jaws is
met by the adoption of friction clutches. (Seepp. 569-70.)

Two shafts slightly out of line but mutually parallel may be
united by the Oldham coupling Fig. 474. A middle plate c, having
cross strips, unites with grooves in the flanges A and B, and the
velocity isl transmitted unimpaired. If the shafts are mutually
inclined, the Hooke's or Universal Joint, A, Fig. 475, must be
employed, and if considerably out of line though parallel, B must
be used. A transmits the velocity unevenly, but the double
arrangement B -rights this difficulty. Fig. 476 was adopted for
many years at a northern establishment: E is the engine, and
u j are universal joints, while the three shafts represent three
separate shops. (See Appendices L and /Z, pp. 763 and 866.)
^ Keys were examined in Figs. 374-5. The sunk key is best,
but the flat key is more often used in shop shafting. Cone Keys
(Fig. 473) are made from a hollow cone, turned and afterwards
divided : they give a very perfect grip.

Keys should have a taper in depth from front to rear, and a
gib-head adopted as in Fig. 477, if there are no means of otherwise
releasing the key. Although some workmen fit keys at top and
bottom only, they should no doubt fit accurately both at top and
sides. Shrinking boss on shaft gives very great security. Keys
are sometimes forged on the shaft. (See p. 423.)

Feather or sliding keys can be fastened either to boss or shaft
as most convenient. See A and B, Fig. 478.

Bearings are strictly gun-metal supports termed bushes, but
the supporting brackets take various forms. Fig. 479 is a
common hanger, Fig. 480 a wall box, and Fig. 482 a wall bracket.
The last two have bearing and bracket separate to allow of adjust-
ment. Fig. 481 shews a special hanger, having a long cast-iron
bearing lying in a spherical seat which adjusts itself automatically
to the shaft deviation. Permanent vertical adjustment is obtained
by screw and nut